Method for Producing Copper-Clad Aluminum Wire

ABSTRACT

A method for producing copper-clad aluminum wire may include providing a round stock of core material, cleaning the core and depositing a barrier material on the core to form a thin film coating of barrier material on the core. The method may include providing one or more strips of a cladding material in continuous form, advancing the coated core and the one or more strips of cladding material, and forming the strips of cladding material to conform around the coated core wherein a cross-sectional area of the coated core is reduced, the formed strips of cladding material forming one or more fins. The method may include quenching the conformed strips of cladding material and the coated core and removing the fins to form a cladding material-clad coated wire or rod.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Patent Application No. PCT/US09/50325, filed on Jul. 10, 2009, designating the U.S. and claiming the benefit of U.S. Provisional Application No. 61/079,449, filed Jul. 10, 2008, the teachings of which applications are fully incorporated herein by reference.

FIELD

The present disclosure relates to a method for the continuous production of clad wire, more particularly, for the manufacture of copper-clad aluminum wire.

BACKGROUND

Copper-clad aluminum wire may provide the conductivity of copper at a lower weight provided by the aluminum core. Aluminum has the advantage of reduced weight compared to the standard copper cables. For the same electrical resistance, the weight of an aluminum conductor is about one half that of a copper conductor. However, adequate bonding at the copper-aluminum interface may often be a problem resulting in mechanical failure as the copper/aluminum interface may be brittle and weak.

One basic approach may be to provide heat into each of the materials and roll form the materials into a round section wherein the copper material surrounds the aluminum material. The combination of heat and roll forming provides a clad wire.

U.S. Pat. No. 3,562,899 describes one method of cladding. The core wire is initially straightened after it comes off the supply reel, and the sheath and core may be cleaned, rinsed and dried in continuous equipment. A series of rolls may form the sheath around the core, with some slight clearance. A welder may then weld the seam, care being taken that the weld does not penetrate the entire sheath, which could alter the metallurgical condition of the core. Sizing rolls may then bring the wire to its final dimensions, and the wire may be either coiled or cut into discrete lengths.

As another example, two strips of Oxygen Free Copper, C10100, may be bonded to either a core of aluminum or a core of steel in a process known as solid cladding. A basic method of manufacturing is disclosed by in U.S. Pat. No. 3,714,701 assigned to Polymetallurgical Corp. Further developments are disclosed by U.S. Pat. No. 4,227,061 assigned to Copperweld Corp. The entire disclosure of each patent is incorporated herein by reference.

Bimetallic wires may be created by combining two different metals into a single conductor. The result may be a low-cost, light-weight alternative to using solid copper. The BiMetals Division of CommScope Inc. manufactures Copper Clad Aluminum (CCA) and Copper Clad Steel (CCS) wire. Bimetallic wire applications may include aerospace, automotive harness, battery cables, RF shielding, telecommunications, electronics, utilities and other industrial applications, for example. The BiMetals Division provides conductors made from CCA and CCS as coaxial cable products.

A number of shortcomings may be found in previous methods of cladding aluminum wire, such as the inability to respond to inline annealing, relatively low mechanical strength, poor bonding of the copper to the aluminum and corrosion.

What is needed is a relatively high speed, continuous process for producing smaller diameter copper-clad aluminum wire which has a metallurgical bond created between the copper cladding and the aluminum core.

SUMMARY

A method is provided for producing a copper-clad aluminum wire from an aluminum round stock and one or more strips of copper flat stock wherein the surface of the aluminum wire is cleaned by exposure to plasma, followed by the deposition of a metallic barrier coat onto the wire. The coated aluminum wire is heated and fed into a retort containing an inert or reducing atmosphere. Copper strips are provided, heated and fed into the retort along opposite sides of the coated wire. The strips and wire engage a rolling mill having rolls of a profile to conform and compress the strips of copper around the coated aluminum wire, leaving fins extending from the clad wire. The clad wire may be quenched and the fins removed.

In an exemplary embodiment, the metal barrier coating may be electroplated nickel. The process may operate in a continuous mode at 200-400 feet per minute. The copper may comprise about 5% to about 20% of the total cross-section of the clad wire. In another embodiment, the copper may comprise about 5% to about 30% of the total cross-section of the clad wire.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description below may be better understood with reference to the accompanying figures which are provided for illustrative purposes and are not to be considered as limiting any aspect of the invention.

FIG. 1 is a flow chart of a method according to the present disclosure;

FIG. 2 is a cross-sectional view of the clad wire prior to removal of the fins; and

FIG. 3 is a schematic process diagram of the method, according to the flow chart of FIG. 1.

DETAILED DESCRIPTION

Turning first to FIG. 2, a copper clad wire 10 is shown in cross-sectional view as it would emerge from forming rolls and a quenching operation, according to the present disclosure. The clad wire 10 includes an aluminum core 20 on which has been deposited a barrier layer 30 of one or more metals, around which two strips 40 of copper flat stock have been formed. Fins 50, which are the result of the forming operation, may next be removed, for instance by skiving, to provide a copper-clad aluminum wire useful in electrical transmission.

The method for producing the copper-clad aluminum wire shown in FIG. 2 is shown in brief form in FIG. 1 and described more fully below.

As shown in Block 100, an aluminum stock may be provided in roll form, as a wire or rod for instance, that may be processed continuously through a series of operations. The aluminum stock may comprise aluminum, such as AA1350 and AA1100 or an aluminum alloy, such as AA6201, but particularly higher strength aluminum alloys, such as 5154. Generally, the aluminum may be in wire form having a diameter of about 0.300 inch to about 0.500 inch.

The aluminum wire may first be straightened and then be exposed (Block 200) to a cleaning operation to remove contaminants and impurities from the surface by exposure to plasma glow discharge. This may next be followed by the deposition of a thin film of a metal or combination of metals onto the plasma-treated surface to form a barrier coating. This thin film may be present at a thickness of about 1 μm to about 1000 μm. The film may include a metal including, but not limited to, nickel, tin, silver, cobalt, phosphorus, zinc and combinations thereof. In an embodiment, the film may include carbon. The thin film of metal may be deposited by plasma, electroplating in a continuous process, depositing by vacuum metallization, sputtering, chemical solution deposition, chemical vapor deposition and/or ion beam deposition.

Copper strips in continuous form may next be provided (Block 300) which may be used to clad the coated aluminum wire. The copper strips may comprise copper and its alloys, such as CDA 101 or CDA 102, oxygen-free coppers. The copper strips may be between about 0.333 inch to about 1.00 inch wide and about 0.003 inch to about 0.040 inch in thickness such that the copper may comprise between about 5% and about 20% of the cross-sectional area of the clad wire. In another embodiment, the copper may comprise between about 5% and about 30% of the cross-sectional area of the clad wire. The strips may be provided as flat stock or in profile form. It is contemplated that other metals could be used to clad the coated wire, including but not limited to, nickel, tin and stainless steel.

The copper strips and coated aluminum wire may be heated, for instance by induction or resistance heating, and introduced into a retort (Block 400) containing an inert or reducing atmosphere where additional cleaning of the surfaces to be contacted may take place. The copper strips may be heated to temperatures of about 300° F. to about 1500° F. The coated aluminum wire may be heated to temperatures of about 300° F. to about 1000° F. The copper strips may be positioned on opposite sides of the coated aluminum wire such that upon forming the strips completely envelop the surface of the coated aluminum wire (see FIG. 2).

The copper strips and coated aluminum wire may next be fed (Block 500) into a rolling mill having rolls of a specific profile wherein the copper strips and coated aluminum wire converge and the copper strips are formed to conform around the coated aluminum wire and into the shape shown in FIG. 2. The rolls may apply a pressure of about 4000 psi to about 20,000 psi. to the heated strips and wire. During this portion of the process, the cross-sectional area of the coated wire may be reduced by about 3% to about 50% to assist in achieving a metallurgical bond between the various metal layers. This forming portion of the process may also take place under an inert or reducing atmosphere.

The clad wire may next be quenched by passing such through, for instance, water or a water/glycol mixture, and cooling the clad wire to a temperature in the range of about 100° F. to about 250° F. The quenching media may be scrubbed of trapped oxygen to reduce the chance of oxidation during the quenching process.

This then provides the cross-section shown in FIG. 2 including the fins 50 formed by the strips of copper wire being formed together and around the coated aluminum wire. The fins may then be removed by skiving or using another cutting device and the copper-clad aluminum wire wound onto a roll or cut to length.

Accordingly, the process for producing copper-clad aluminum wire may be carried out in a continuous fashion. Because there is no welding step in this process, the rate of production may be about 200 feet per minute to about 400 feet per minute of copper-clad wire. The copper-clad wire may have a diameter of about 0.032 inch to about 0.325 inch. In an embodiment, the copper-clad wire may have a diameter of about 0.032 inch to about 0.375 inch.

FIG. 3 is a schematic process diagram, according to the method described above, illustrating a system and apparatus for carrying out the method of forming copper-clad aluminum wire wherein the wire has a metallic barrier coating. The system may include a source 302 of round stock core material 304. For example, the round stock core material 304 may be wire and may include aluminum. The system may include a straightener 306 configured to straighten the round stock core 304. The system may include one or more DC rectifiers 308 a-308 d, configured to heat a component, e.g., core 304. The system may include a cleaner 310, rinse 312 and a coating apparatus 314, configured to clean and rinse a surface of the round stock core 304 and to apply a barrier coating of a metal resulting in a coated core 316. The coated core 316 may be heated, e.g., by induction heating 322.

The system may include a source of one or more strips, e.g., strips 318 a, 318 b, of a cladding material. The cladding material may include copper. The one or more strips 318 a, 318 b of cladding material may be heated by resistance heating using, e.g., DC rectifiers 308 c and 308 d. The system may include a retort 320 configured to provide an inert or reducing atmosphere. The system may include a rolling mill 322 configured to form the one or more strips 318 a, 318 b around the coated core 316. Although not shown in FIG. 3, the system may include a quenching apparatus and a fin-cutting apparatus configured to cool the cladding material-clad coated core and to remove fins formed in the rolling mill, respectively. The system may include a roll 328 configured to receive a copper-clad aluminum wire 326 that may be then be wound about the roll 328.

The process as indicated above may provide a lightweight copper-clad wire capable of being drawn, in-line annealed and manufactured like a solid copper wire but substantially lighter in weight due to the aluminum core. In addition, by including the cleaning steps and barrier coat in the manufacturing process, the copper and aluminum may be metallurgically combined to reduce the formation of undesirable alloy or intermetallic structures.

Although two copper strips 40 have been shown and described, as few as one and more than two such strips may be formed around the coated aluminum wire. Accordingly, many modifications and other embodiments of the invention will come to the mind of one skilled in the art having the benefit of the teachings presented in the foregoing description. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed, and that modifications and embodiments are intended to be included.

According to one aspect of the present disclosure, there is provided a method for producing copper-clad aluminum wire. The method includes providing a round stock core material comprising aluminum, wherein the round stock core is a rod or wire; straightening the core and cleaning the core using plasma glow discharge. The method further includes depositing a barrier coating on the core wherein the coating is a thin film and the coating includes a metal or carbon; providing one or more strips of cladding material in a continuous form, the cladding material including copper, nickel, tin or stainless steel. The method includes heating the coated aluminum core and the one or more strips of copper cladding material; advancing the heated coated aluminum core and the one or more heated strips of copper cladding material into a retort, the retort containing a heated inert or reducing atmosphere. The method further includes roll-forming the one or more strips of copper cladding material to conform around the coated aluminum core forming a copper-clad coated aluminum core, the roll-forming including applying a pressure to the heated strips and heated coated core wherein a cross-sectional area of the coated aluminum core is reduced and the heated strips of cladding material form one or more fins. The method further includes quenching the copper-clad coated aluminum core in a cooling liquid, removing the fins; and winding the copper-clad coated aluminum core onto a roll or cutting to a length wherein the cladding includes between about 5% and about 30% of a cross-sectional area of the copper-clad coated aluminum core.

According to another aspect of the disclosure, there is provided a method for producing copper-clad aluminum wire. The method includes providing a round stock of core material wherein the round stock is a rod or wire; cleaning the core; and depositing a barrier material on the core to form a thin film coating of barrier material on the core. The method further includes providing one or more strips of a cladding material in continuous form; advancing the coated core and the one or more strips of cladding material; forming the strips of cladding material to conform around the coated core wherein a cross-sectional area of the coated core is reduced, the formed strips of cladding material forming one or more fins. The method further includes removing the fins to form a cladding material-clad coated wire or rod.

According to yet another aspect of the disclosure, there is provided a system for producing cladding material-clad coated wire. The system includes a source of round stock core material configured to provide a core to a straightener; the straightener configured to straighten the core; a cleaner configured to clean the core; and a coating apparatus configured to deposit a barrier coating on the cleaned core. The system further includes a source of cladding material configured to provide one or more strips of cladding material; one or more heating apparatuses configured to heat the coated core and the one or more strips of cladding material; a retort configured to provide an inert or reducing atmosphere; and a rolling mill configured to form the one or more strips of the cladding material around the coated core wherein a cross-sectional area of the coated core is reduced. The system further includes a quenching apparatus configured to cool the cladding material-clad coated core; a fin-cutting apparatus configured to remove fins formed in the rolling mill; and a roll configured to receive the cladding material-clad coated core. 

1. A method for producing cladding material-clad aluminum wire, the method comprising: providing a round stock core material comprising aluminum, wherein the round stock core is a rod or wire; cleaning the core using plasma glow discharge; depositing a thin film barrier coating on the core, the coating comprising a metal or carbon; providing one or more strips of cladding material in a continuous form, the cladding material comprising copper, nickel, tin or stainless steel; heating the coated aluminum core and the one or more strips of cladding material; advancing the heated coated aluminum core and the one or more heated strips of cladding material into a retort, the retort containing a heated inert or reducing atmosphere; roll-forming the one or more strips of cladding material to conform around the coated aluminum core forming a cladding material-clad coated aluminum core, the roll-forming comprising applying a pressure to the heated strips and heated coated core wherein a cross-sectional area of the coated aluminum core is reduced and the heated strips of cladding material form one or more fins; quenching the copper-clad coated aluminum core in a cooling liquid; and removing the fins, wherein the cladding comprises between 5% and 30% of a cross-sectional area of the cladding material-clad coated aluminum core.
 2. A method for producing cladding material-clad wire, the method comprising: providing a round stock of core material wherein the round stock is a rod or wire; cleaning the core; depositing a barrier material on the core to form a thin film coating of barrier material on the core; providing one or more strips of a cladding material in continuous form; advancing the coated core and the one or more strips of cladding material; forming the strips of cladding material to conform around the coated core wherein a cross-sectional area of the coated core is reduced, the formed strips of cladding material forming one or more fins; and removing the fins to form a cladding material-clad coated wire or rod.
 3. The method of claim 2 wherein the forming comprises: heating the strips and the coated core; introducing the strips and the coated core into a retort; positioning the one or more strips around the coated core such that upon forming, the strips envelop a surface of the coated core; and rolling the strips and the coated core so that the strips are formed to conform around the coated core and resulting in the one or more fins.
 4. The method of claim 3 wherein the retort contains an inert or reducing atmosphere.
 5. The method of claim 3 wherein the rolling comprises applying a pressure of 4000 psi to 20,000 psi to the strips and the coated core.
 6. The method of claim 2 further comprising winding the cladding material-clad coated wire onto a roll or cutting the cladding material-clad coated wire or rod to a length.
 7. The method of claim 2 wherein the core material comprises aluminum.
 8. The method of claim 2 wherein the core is a rod or wire and has a diameter of 0.300 inch to 0.500 inch.
 9. The method of claim 2 wherein the cleaning comprises plasma glow discharge.
 10. The method of claim 2 wherein the barrier material comprises a metal.
 11. The method of claim 2 wherein the barrier material comprises carbon.
 12. The method of claim 2 wherein the depositing comprises plasma deposition, electroplating, vacuum metallization, sputtering, chemical solution deposition, chemical vapor deposition or ion beam deposition.
 13. The method of claim 2 wherein the thin film has a thickness of 1 μm to 1000 μm.
 14. The method of claim 2 wherein the cladding material comprises copper, nickel, tin or stainless steel.
 15. The method of claim 2 wherein the cladding material comprises between 5% and 30% of a cross-sectional area of the cladding material-clad coated wire or rod.
 16. The method of claim 2 further comprising quenching the conformed strips of cladding material and the coated core.
 17. The method of claim 16 wherein quenching comprises cooling the clad coated core to a temperature in the range of 100° F. to 250° F.
 18. The method of claim 2 wherein a rate of production of clad coated wire or rod is between 200 feet per minute and 400 feet per minute.
 19. The method of claim 2 wherein the clad coated wire or rod has a diameter between 0.032 inch to 0.375 inch.
 20. A system for producing cladding material-clad coated wire, the system comprising: a source of round stock core material configured to provide a core to a straightener; the straightener configured to straighten the core; a cleaner configured to clean the core; a coating apparatus configured to deposit a thin film barrier coating on the cleaned core; a source of cladding material configured to provide one or more strips of cladding material; one or more heating apparatuses configured to heat the coated core and the one or more strips of cladding material; a retort configured to provide an inert or reducing atmosphere; a rolling mill configured to form the one or more strips of the cladding material around the coated core wherein a cross-sectional area of the coated core is reduced; a quenching apparatus configured to cool the cladding material-clad coated core; and a fin-cutting apparatus configured to remove fins formed in the rolling mill. 